In dental therapy, it is known and customarily the practice to make plaque easily distinguishable by painting a fluorescible solution on the teeth and then exciting it to fluorescent radiation by means of suitable lamps. Plaque is the coating on the teeth which consists mainly of bacteria and causes disease of the teeth and gums, and normally is invisible. It has been shown that fluorescible material only or at least preferably remains adhered to the plaque, but not to the clean and healthy teeth and parts of the teeth. The same goes for those parts on which tartar has formed by mineralization of the plaque or which already have been attacked by dental decay. Thus, these critical or respectively diseased parts of the teeth may in a simple manner be made visible and located by the foregoing checking treatment and procedure, since only these parts fluoresce under illumination and hence are brought into sharp relief against the other non-fluorescent regions. In addition, by the fluorescent effect, diseased places on the gums as well as other diseased regions of skin and tissue can also be made visible.
A test lamp has been proposed for the purpose described and utilizes an incandescent lamp as light source, together with a dichroic reflector behind the lamp and a dichroic filter in front of the lamp as well as preferably another dichroic observation mirror which has the same transmission and reflection characteristics as the filter. In that way the radiation available for illumination of the parts to be tested is restricted essentially to blue light which particularly excites a fluorescin solution; and, as far as possible, only a little radiation is emitted having those wave lengths which correspond with the color of the yellow or green fluorescent radiation. Only in this manner can a significant contrast be achieved between the fluorescing regions and their non-fluorescing surroundings. Otherwise the non-fluorescing surroundings under illumination with the light of the fluorescent radiation would appear approximately of the same hue as the latter.
The known test-lamp is costly to produce and consequently is relatively expensive. It is complicated in construction and also troublesome to handle. Furthermore, the user must always be concerned that the fluorescent material too, which is indispensable and normally in liquid form, is always handily available. For these reasons the test-lamp does not fulfill those prerequisites which would favor an otherwise wide distribution amongst the consuming public interested in oral hygiene and regular self-checking of the condition of the mouth particularly teeth and gums.